U.S. patent application number 11/976703 was filed with the patent office on 2008-06-19 for golf club head.
This patent application is currently assigned to SRI Sports Limited. Invention is credited to Takashi Nakano.
Application Number | 20080146375 11/976703 |
Document ID | / |
Family ID | 39528045 |
Filed Date | 2008-06-19 |
United States Patent
Application |
20080146375 |
Kind Code |
A1 |
Nakano; Takashi |
June 19, 2008 |
Golf club head
Abstract
A hollow golf club head having a face portion, a crown portion,
a sole portion, a side portion and a hosel portion comprises: a
face component made of a titanium alloy and forming a major part of
the face portion; a hosel-and-heel component made of a titanium
alloy and forming a heel-side part of the sole portion and side
portion and the hosel portion; and a rear component made of a
magnesium alloy and forming a rear part of the head. The
above-mentioned heel-side part of the sole portion formed by the
hosel-and-heel component extends towards the toe of the head and
intersects a vertical straight line passing through the center of
gravity of the club head so as to form a major part of the sole
portion.
Inventors: |
Nakano; Takashi; (Kobe-shi,
JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
SRI Sports Limited
|
Family ID: |
39528045 |
Appl. No.: |
11/976703 |
Filed: |
October 26, 2007 |
Current U.S.
Class: |
473/350 ;
473/345 |
Current CPC
Class: |
A63B 53/0466 20130101;
A63B 53/0433 20200801; A63B 53/047 20130101; A63B 2053/0491
20130101; A63B 2209/00 20130101; A63B 53/0412 20200801; A63B
53/0408 20200801; A63B 53/02 20130101; A63B 53/04 20130101; A63B
53/0416 20200801; A63B 2209/10 20130101 |
Class at
Publication: |
473/350 ;
473/345 |
International
Class: |
A63B 53/04 20060101
A63B053/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 19, 2006 |
JP |
2006-341614 |
Claims
1. A golf club head having a face portion of which front face
defines a clubface, a crown portion intersecting the clubface at
the upper edge thereof, a sole portion intersecting the clubface at
the lower edge thereof, a side portion between the crown portion
and sole portion which extends from a toe-side edge to a heel-side
edge of the clubface through the back face of the club head, and a
hosel portion having a shaft inserting hole, and comprising a face
component made of a titanium alloy and forming a major part of the
face portion, a hosel-and-heel component made of a titanium alloy
and forming the hosel portion and a heel-side major part of the
sole portion, and a rear component made of a magnesium alloy,
wherein said heel-side major part of the sole portion formed by the
hosel-and-heel component extends towards the toe of the head to
intersect a vertical straight line passing through the center of
gravity of the club head.
2. The golf club head according to claim 1, wherein the extreme end
of said heel-side part in the heel-and-toe direction of the head is
at a distance in a range of 5 to 40 mm in the heel-and-toe
direction from the intersecting point of said vertical straight
line and said heel-side part.
3. The golf club head according to claim 1, wherein the size of
said heel-side part in the back-and-forth direction is in a range
of 20 to 80 mm.
4. The golf club head according to claim 1, which further comprises
a strip-shaped weighting component, and the weighting component is
made of a material having a specific gravity larger than that of
said magnesium alloy, and disposed along a surface of the rear
component from a toe-side point to a heel-side point on the
surface.
5. The golf club head according to claim 2, wherein the size of
said heel-side part in the back-and-forth direction is in a range
of 20 to 80 mm.
6. The golf club head according to claim 2, which further comprises
a strip-shaped weighting component, and the weighting component is
made of a material having a specific gravity larger than that of
said magnesium alloy, and disposed along a surface of the rear
component from a toe-side point to a heel-side point on the
surface.
7. The golf club head according to claim 3, which further comprises
a strip-shaped weighting component, and the weighting component is
made of a material having a specific gravity larger than that of
said magnesium alloy, and disposed along a surface of the rear
component from a toe-side point to a heel-side point on the
surface.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a golf club head, more
particularly to a hollow structure made of a titanium alloy and a
magnesium alloy.
[0002] In recent years, large-sized wood-type hollow golf club
heads are widely used. The weight of a golf club head naturally has
an upper limit, therefore, in the case of a large-sized golf club
head, the weight margin which can be utilized to optimize the
weight distribution or to adjust the positions of the center of
gravity and sweet spot and the like, becomes decreased. Thus, the
design freedom with respect to the weight distribution is
decreased.
[0003] In order to solve such problem, a hybrid hollow golf club
has been proposed, wherein the main body of the head which is made
of a metal material, is provided in the crown portion with an
opening in order to reduce the weight, and the opening is closed by
a light-weight FRP cover. Such a metal/FRP hybrid head is excellent
at design freedom with respect to the weight distribution. However,
since the internal energy loss of FRPs or fiber reinforced resins
is very large when compared with metal materials, the ball hitting
sound becomes dull, and the tone becomes low, further, the decay
becomes fast. Therefore, the ball hitting sound of the hybrid heads
is usually not preferred by many golfers.
[0004] In the US patent application publication No. US
2006-014592-A1, a hollow golf club head is disclosed, wherein a
main body of the club head made of a titanium alloy is provided
with an opening, and the opening is covered with a thin plate of a
magnesium alloy. In this technique, as the covering plate is not a
fiber reinforced resin, a preferable hitting sound may be obtained.
But, when the size of the main body is considered, the covering
plate is small, therefore, it is difficult to increase the weight
margin.
SUMMARY OF THE INVENTION
[0005] It is therefor, an object of the present invention to
provide a golf club head, which has a hollow structure capable of
increasing the weight margin, without deteriorating the ball
hitting sound.
[0006] According to the present invention, a golf club head having
a face portion, a crown portion, a sole portion, a side portion and
a hosel portion comprises
[0007] a face component made of a titanium alloy and forming a
major part of the face portion,
[0008] a hosel-and-heel component made of a titanium alloy and
forming the hosel portion and a heel-side part of the sole portion
and side portion, and
[0009] a rear component made of a magnesium alloy and forming a
rear part of the head, wherein
[0010] the heel-side part of the sole portion formed by the
hosel-and-heel component extends towards the toe of the head and
intersects a vertical straight line passing through the center of
gravity of the club head so as to form a major part of the sole
portion.
[0011] In this specification, unless otherwise noted, dimensions,
positions and the like relating to the head refer to those under
the standard state of the club head.
[0012] The standard state is such that the club head is set on a
horizontal plane HP so that the axis of the clubshaft(not shown) is
inclined at the lie angle while keeping the axis on a vertical
plane, and the clubface forms its loft angle with respect to the
horizontal plane HP. Incidentally, in the case of the club head
alone, the center line of the shaft inserting hole 7a can be used
instead of the axis of the clubshaft.
[0013] The sweet spot s is the point of intersection between the
clubface 2 and a straight line N drawn normally to the clubface 2
passing the center of gravity G of the head.
[0014] The back-and-forth FB direction is a direction parallel with
the straight line N projected on the horizontal plane HP.
[0015] The heel-and-toe direction is a direction parallel with the
horizontal plane HP and perpendicular to the back-and-forth
direction.
[0016] The moment of inertia is the lateral moment of inertia
around a vertical axis passing through the center of gravity G in
the standard state.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a perspective view of a golf club head according
to the present invention.
[0018] FIG. 2 is an exploded perspective view thereof.
[0019] FIG. 3 is a top view of the golf club head.
[0020] FIG. 4 is a bottom view thereof.
[0021] FIG. 5 is a right side view thereof.
[0022] FIG. 6 is a rear view thereof.
[0023] FIG. 7 is a cross sectional view taken along line x-x in
FIG. 4.
[0024] FIG. 8 is a cross sectional view taken along line Y-Y in
FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] Embodiments of the present invention will now be described
in detail in conjunction with accompanying drawings.
[0026] In the drawings, golf club head 1 according to the present
invention is a hollow head for a wood-type golf club such as driver
(#1) or fairway wood, and the head 1 comprises: a face portion 3
whose front face defines a club face 2 for striking a ball; a crown
portion 4 intersecting the club face 2 at the upper edge 2a
thereof; a sole portion 5 intersecting the club face 2 at the lower
edge 2b thereof; a side portion 6 between the crown portion 4 and
sole portion 5 which extends from a toe-side edge 2c to a heel-side
edge 2d of the club face 2 through the back face BF of the club
head; and
[0027] a hosel portion 7 at the heel side end of the crown to be
attached to an end of a club shaft (not shown).
[0028] Thus, the club head 1 is provided with a hollow (i) and a
shell structure with the thin wall.
[0029] As shown in FIG. 2, the hosel portion 7 comprises a neck
part 7r and a tubular part 7b. The neck part 7r forms a part of the
outer surface of the head. The tubular part 7b extends into the
hollow (i) from the neck part 7r to form a major part of a shaft
inserting hole 7a into which the club shaft is inserted. The
tubular part 7b in this example reaches to the sole portion.
[0030] In the case of a wood-type club head for a driver (#1), it
is preferable that the head volume is set in a range of not less
than 380 cc, preferably not less than 400 cc more preferably not
less than 420 cc in order to increase the moment of inertia and the
depth of the center of gravity. However, to prevent an excessive
increase in the club head weight and deteriorations of swing
balance and durability and further in view of golf rules or
regulations, the head volume is preferably set in a range of not
more than 470 cc, preferably not more than 460 cc.
[0031] The mass of the club head 1 is preferably set in a range of
not less than 180 grams, preferably not less than 185 grams in view
of the strength, swing balance and traveling distance of the ball,
but not more than 220 grams, preferably not more than 215 grams in
view of the directionality and traveling distance of the ball.
[0032] The club head 1 is as shown in FIG. 2, composed of [0033] a
face component 1A made of a titanium alloy, [0034] a hosel-and-heel
component 1B made of a titanium alloy, [0035] a rear component 1C
made of a magnesium alloy and [0036] an optional weighting
component 1D.
Face Component 1A
[0037] The face component 1A is to form a major part of the face
portion 3 including the sweet spot S. Here, the major part means
that 50% or more of the area of the club face 2 is included. Thus,
in order to provide strength, a titanium alloy having a high
specific tensile strength as well as good workability is used. For
example, a beta titanium alloy excellent in strength or alpha-beta
titanium alloy excellent in castability is used. More specifically,
Ti-6Al-4V, Ti-15V-3Cr-3Al-3Sn, Ti-22V-4A1, Ti-15Mo-5Zr-3A1,
Ti-13V-11Cr-3Al, Ti-8Mo-8V-2Fe-3Al, Ti-3Al-8V-6Cu-4Mo-4Zr,
Ti-11.5Mo-6Zr-4.5Sn, Ti-15Mo-5Zr and the like can be preferably
used.
[0038] In this example, the face component 1A forms the entirety of
the face portion 3.
[0039] The thickness tf of the face portion 3 is preferably set in
a range of not less than 1.5 mm, more preferably not less than 2.0
mm, but not more than 5.0 mm, more preferably not more than 4.0 mm,
still more preferably not more than 3.5 mm. The thickness tf in
this embodiment is substantially constant. But, it is also possible
to provide the face portion 3 with a thinner part or parts
surrounding the resultant thicker central part to achieve the
durability and rebound performance.
[0040] Further, the face component 1A in this example, includes
turnbacks 9a, 9b, 9c and 9d.
[0041] The turnbacks 9a, 9b, 9c and 9d extend backwards from the
edges 2a, 2b, 2c and 2d of the club face 2 or face portion 3,
respectively, and the turnbacks form front parts of the crown
portion 4, sole portion 5 and side portion 6. In order to
accommodate the hosel portion 7, a heel-side part of the upper
turnback 9a is cut off by an arc. Owing to the turnbacks, stress
occurring at the junction when hitting a ball is decreased and the
durability can be improved. If the size of the turnbacks is too
large however, it is difficult to obtain an efficient weight margin
and further it is difficult to make it by press molding. Therefore,
excepting the above-mentioned cut-off part, the size F of the
turnbacks 9 in the back-and-forth direction of the club head is set
in a range of not less than 3 mm, preferably not less than 5 mm,
more preferably not less than 7 mm, but not more than 30 mm,
preferably not more than 25 mm, more preferably not more than 20
mm.
[0042] In this example, the turnback is formed along the almost
entire length of the peripheral edge of the club face 2. But, the
turnback may be formed along only a part of the peripheral edge of
the club face 2, for example, only the upper edge 2a and lower edge
2b. Further, the face component 1A may be made up of the face
portion 3 only, namely, there is no turnback.
[0043] The face component 1A inclusive of the turnbacks has a
one-piece structure formed by press molding of a rolled plate in
view of the production efficiency and strength. It is of course
possible to form such one-piece structure by forging of a rolled
plate, casting of the alloy, or the like.
Hosel-and-Heel Component 1B
[0044] As shown in FIG. 2 and FIG. 5, the hosel-and-heel component
1B includes: the above-mentioned hosel portion 7; a heel-side sole
plate 10 forming a heel-side part of the sole portion 5; and a
heel-side side plate 11 forming a heel-side part of the side
portion 6.
[0045] As show in FIG. 4, the heel-side sole plate 10 extends to at
least the point SG which is an intersecting point of a vertical
straight line passing the center G of gravity of the head with the
outer surface of the sole portion 5 under the standard state of the
head.
[0046] As shown in FIG. 5, the heel-side side plate 11 extends from
the underside of the neck part 7r of the hosel portion 7 to the
heel-side sole plate 10, defining a part of the outer surface of
the head, and the horizontal width w thereof measured between the
front edge and the rear edge is progressively increased from the
crown portion to the sole portion. Between the heel-side side plate
11 and the hosel tubular part 7b, a gap may be formed, but in this
example, there is no gap, therefore, the heel-side side plate 11
functions as a stay for the hosel tubular part 7b.
[0047] The hosel portion 7 is subjected to a large torsional moment
during down swing, and the heel-side part of the sole portion 5
between the heel and the intersecting point SG is very liable to
contact with the ground surface, therefore, in order to provide the
strength and rigidity, the hosel-and-heel component 1B has a
one-piece structure made of the titanium alloy.
[0048] As the titanium alloy of the hosel-and-heel component 1B,
the above-mentioned titanium alloys listed in connection with the
face component 1A can be used too. The titanium alloy of the
hosel-and-heel component 1B can be the same as or different from
the titanium alloy of the face component 1A.
[0049] In view of the shape of the hosel-and-heel component 1B
which is complex when compared with the face component 1A, it is
preferred that the hosel-and-heel component 1B is formed by
casting. In this case, accordingly, titanium alloys suitable for
casting such as Ti-6Al-4V are used.
[0050] The front edge of the heel-side side plate 11 is connected
with the rear edge of the heel-side turnback 9d of the face
component 1A. The front edge of the heel-side sole plate 10 is
connected with the rear edge of the lower turnback 9b.
[0051] As shown in FIG. 4, the size (b) of the heel-side sole plate
10 measured in the back-and-forth direction FB from the front edge
is preferably set in a range of not less than 20 mm, more
preferably not less than 30 mm in order to provide the sole portion
5 with a resistance to scratch, but preferably not more than 80 mm,
more preferably not more than 60 mm, still more preferably not more
than 50 mm. If the size (b) is too large, as the rear component 1C
becomes smaller accordingly, it becomes difficult to obtain an
efficient weight margin.
[0052] The rear edge 10e2 of the heel-side sole plate 10 and the
rear edge of the heel-side side plate 11 are connected with the
edge of the rear component 1C.
[0053] The rear edge 10e2 in this example is straight and
substantially parallel to the heel-and-toe direction. Aside from
such a straight configuration, various configurations such as arc,
wave and zigzag can be employed.
[0054] In this example, the toe-side edge 10e1 of the heel-side
sole plate 10 is straight and substantially parallel to the
back-and-forth direction FB. Aside from such a straight
configuration, various configurations such as arc, wave and zigzag
can be employed.
[0055] Preferably, the extreme end (toe-side edge 10e1) of the
heel-side sole plate 10 is spaced apart from the intersecting point
SG by a distance (a) of not less than 5 mm, preferably not less
than 10 mm towards the toe. However, if the distance (a) is
excessively large, it becomes difficult to obtain an effective
weight margin. Therefore, the distance (a) is preferably not more
than 40 mm, more preferably not more than 30 mm, still more
preferably not more than 20 mm.
[0056] As shown in FIG. 7 and FIG. 8, the thickness ts of the
heel-side sole plate 10 is preferably set in a range of not less
than 0.4 mm, more preferably not less than 0.5 mm, but not more
than 3.0 mm, more preferably not more than 2.5 mm, still more
preferably not more than 2.0 mm.
[0057] In order to connect the face component 1A with the
hosel-and-heel component 1B, welding, soldering and/or adhesive
bonding can be employed. But, in view of the joint strength and
production efficiency, welding such as plasma welding, Tig welding
and laser welding is especially preferred.
[0058] In order to facilitate positioning of one of the components
1A and 1B relatively to the other during welding, at least one of
them is provided with hooks 12 as shown in FIG. 2. In this example,
the hooks 12 are provided on the front edge of the heel-side sole
plate 10, and the hooks include inner hooks 12A and outer hook(s)
12B alternately arranged along the edge. The inner hook 12A is to
support and position the inner surface of the edge to be jointed.
The outer hook 12B is to support and position the outer surface of
the edge to be jointed.
Rear Component 1C
[0059] The rear component 1C is made of the magnesium alloy and has
the largest outer surface area in the components 1A-1C in order to
obtain a large weight margin. The rear component 1C in this example
is a casting of the magnesium alloy.
[0060] In order to achieve weight reduction while preventing a
significant decrease in the club head strength, the specific
gravity of the magnesium alloy is preferably not less than 1.6,
more preferably not less than 1.7, but not more than 2.0, more
preferably not more than 1.9. Further, in view of the strength and
workability, magnesium alloys including Al and Zn are preferably
used. Accordingly, the specific gravity of the rear component 1C is
smaller than those (typically 4.4 to 4.8) of the face component 1A
and hosel-and-heel component 1B.
[0061] The rear component 1C is attached to the rear edge of the
assembly of the face component 1A and the hosel-and-heel component
1B, whereby the rear component 1C forms the remaining rear parts of
the crown portion 4, side portion 6 and sole portion 5. More
specially, the rear component 1C forms: [0062] a rear part 4B of
the crown portion 4 connected with the upper turnback 9a of the
face component 1A; [0063] a rear part 6B of the side portion 6
connected with the toe-side turnbacks 9c of the face component 1A
and connected with the heel-side side plate 11 of the
hosel-and-heel component 1B; and [0064] a rear part 5B of the sole
portion 5 connected with the heel-side sole plate 10 and the lower
turnback 9b.
[0065] In order to accommodate the neck part 7r of the hosel
portion 7, the front edge of the rear component 1C is cut off by an
arc.
[0066] The thickness tc of the rear part 4B of the crown portion 4
is preferably set in a range of not less than 0.3 mm, more
preferably not less than 0.4 mm, but not more than 3.0 mm, more
preferably not more than 2.0 mm, still more preferably not more
than 1.5 mm.
[0067] The thickness tp of the rear part 6B of the side portion 6
is preferably set in a range of not less than 0.4 mm, more
preferably not less than 0.5 mm, but not more than 3.0 mm, more
preferably not more than 2.5 mm.
[0068] As shown in FIG. 2 and FIG. 7, the front edge 1Ce of the
rear component 1C to be jointed with the face component 1A and
hosel-and-heel component 1B is provided with an overlapping part 15
substantially continuously along the edge 1Ce. The outer surface of
the overlapping part 15 is stepped from the outer surface of the
clubs head by an amount corresponding to the thickness of the rear
edge of the assembly.
[0069] The overlapping part 15 is overlap jointed with the rear
edge of the assembly of the face component 1A and hosel-and-heel
component 1B. Preferably, the size Wu of the overlapping part 15
measured in the back-and-forth direction from the front edge to the
rear edge is set in a range of not less than 1.0 mm, more
preferably not less than 1.5 mm, but not more than 10.0 mm, more
preferably not more than 5.0 mm.
[0070] In this embodiment, the rear component 1C is fixed to the
assembly by the use of an adhesive agent applied between the edge
and the overlapping part 15. As to the adhesive agent, for example,
cold-curing two-component epoxy resin adhesives, heat-curing
one-component epoxy resin adhesives, two-component modified
acrylate adhesive, and two-component acrylic adhesive can be used.
Especially, a cold-curing two-component epoxy resin adhesive is
preferred for the excellent shear strength and peel strength.
[0071] As has been explained, a major part of the club head 1 is
formed by the magnesium alloy, therefore the weight margin is
increased, without deteriorating the ball hitting sound because a
FRP component is not used as a major component. Utilizing the
increased weight margin a relatively heavy weighting component 1D
can be disposed.
[0072] The weighting component 1D may be made of a metal material
having a specific gravity larger than that of the magnesium alloy
of the rear component 1C. Preferably, the specific gravity of the
weighting component 1D is set in a range of not less than 7.0, more
preferably not less than 10.0, still more preferably not less than
12.0, but not more than 20.0, more preferably not more than 19.0,
still more preferably not more than 18.0. For example, stainless
steels, tungsten, tungsten alloys, copper alloys, nickel alloys and
the like can be used. In particular, tungsten-nickel alloys are
preferred for the large specific gravity and lower material
cost.
[0073] In this embodiment, the weighting component 1D having a
shape of tape or ribbon is disposed along the outer surface of the
side portion 6 of the rear component 1C. In this case, as shown in
FIG. 7 and FIG. 8, the outer surface is preferably provided with a
recessed part 22 accommodated to the weighting component 1D, and
the weighting component 1D is fitted in the recessed part 22 and
bonded thereto by the use of an adhesive agent.
[0074] The weighting component 1D in this example extends
continuously between its toe-side end 17 and heel-side end 18
through the back face BF, and includes a part WV waving in the
up-and-down direction as best shown in FIG. 6.
[0075] From the toe-side end 17 located at a relatively lower
position, this wave part wv is gradually going up towards the back
face BF, and at the rear end of the club head, it reaches to its
peak 20 and most approaches to the boundary (e) between the crown
portion 4 and side portion 6. Then, the wave part is gradually
going down towards the heel, and reaches to its lowest point and
then again going up until the heel-side end 18. Thus, the weighting
component 1D in this example runs at a higher position on the
backside BF of the head, but lower positions on the toe-side and
heel-side. As a result, the center of gravity becomes deeper and
lower and the moment of inertia can be increased.
* Comparison Tests
[0076] Wood golf club heads (EX. 1 to 5, Ref. 1 to 3) of the same
shape and same size (volume: 460 cc, Loft angle: 11 degrees, Lie
angle: 57 degrees) were prepared and attached to identical FRP
shafts (SRI sports Ltd. "MP00", flex R) to make 45-inch wood clubs,
and the following comparison tests were conducted.
[0077] Each of the heads was made based on the structure shown in
FIG. 1 to FIG. 8, and comprised a face component, a hosel-and-heel
component and a rear component as explained above, and the face
component and hosel-and-heel component were connected with each
other by means of plasma welding, and then the assembly was fixed
to the rear component by means of an adhesive agent.
<Face Component>
[0078] In Ex. 1 to Ex. 5 and Ref. 2 to Ref. 3, the face component
was made of a titanium alloy having a specific gravity of 4.54 and
comprising 4.0% of Al, 2.5% of V, 1.8% of Mo 1.7% of Fe and the
balance being essentially Ti.
[0079] In Ref. 1, the face component was made of a titanium alloy
having a specific gravity of 4.42 and comprising 6.0% of Al, 4.0%
of V, and the balance being essentially Ti.
[0080] In each head, the face component was formed by die punching
a rolled plate of the titanium alloy and then press molding the
punched-out plate. The thickness tf of the face portion was 3.2 mm.
The size F of the turnbacks was 10 mm.
<Hosel-and-Heel Component>
[0081] In EX. 1 to EX. 15 and Ref. 1 and Ref. 3, the hosel-and-heel
component was made of a titanium alloy having a specific gravity of
4.42 and comprising 6.0% of Al, 4.0% of V, and the balance being
essentially Ti.
[0082] In Ref. 2, the hosel-and-heel component was made of a
magnesium alloy having a specific gravity of 1.81 and comprising
8.4% of Al, 0.6% of Zn, 0.3% of Mn and the balance being
essentially Mg.
[0083] In each head, the hosel-and-heel component was formed by
lost-wax precision casting. The thickness ts of the heel-side sole
plate was 0.8 mm.
<Rear Component>
[0084] In Ex. 1 to Ex. 5 and Ref. 2 and Ref. 3, the rear component
was made of a magnesium alloy having a specific gravity of 1.81 and
comprising 8.4% of Al, 0.6% of Zn, 0.3% of Mn and the balance being
essentially Mg.
[0085] In Ref. 1, the rear component was made of a titanium alloy
having a specific gravity of 4.42 and comprising 6.0% of Al, 4.0%
of V, and the balance being essentially Ti.
[0086] In each head, the rear component was formed by lost-wax
precision casting. The thickness tc of the crown portion was 1.0
mm. The thickness tp of the rear part 6B of the side portion was
1.0 mm. The thickness of the rear part 5B of the sole portion was
1.0 mm.
<Weighting Component>
[0087] In Ex. 5, the weighting component made of a tungsten-nickel
alloy was disposed.
Measurement of Weight of Hollow Structure
[0088] The weight of the face component, hosel-and-heel component
and rear component was measured and the results are indicated by an
index based on Ref. 1 being 100, wherein the smaller the value, the
larger the weight margin.
Carry Distance Test
[0089] Each of the wood clubs was mounted on a swing robot, and hit
three-piece balls ("XXIO" of SRI sports Ltd.) five times at the
head speed of 40 m/s to obtain the average carry distance. The
results are indicated in Table 1 by an index based on Ref. 1 being
100, wherein the larger the value, the longer the carry
distance.
Sole Scratch Resistance Test
[0090] Increasing the head speed to 50 m/s, each of the wood clubs
mounted on the swing robot hit the three-piece balls 500 times at
the sweet spot 5. Thereafter, by the naked eye, the sole portion
was checked for scratch and ranked in the order of less scratch,
wherein the smaller the rank number, the better the scratch
resistance.
Durability Test
[0091] After the scratch resistance test, the hitting test was
continued up to 5000 times at the maximum, and every 100 hits the
head was checked on the whole by the naked eye. If any damage was
found, the test was stopped and the total number of the hits was
recorded.
Directionality Test
[0092] Each of five golfers having handicap ranging from 5 to 15
hit the golf balls five times per each club and the difference from
the target trajectory was measured. The results are indicated by an
index based on Ref. 1 being 100, wherein the larger the value, the
better the directionality of a hit ball.
[0093] The test results are shown in Table 1.
TABLE-US-00001 TABLE 1 Club head Ref. 1 Ref. 2 Ref. 3 Ex. 1 Ex. 2
Ex. 3 Ex. 4 Ex. 5 Hollow structure Face component Ti Ti Ti Ti Ti Ti
Ti Ti Material Rear component Ti Mg Mg Mg Mg Mg Mg Mg Material
Hosel-&-heel component Ti Mg Ti Ti Ti Ti Ti Ti Material
Distance a (mm) *1 -- -- -10 0 10 30 40 10 Size b (mm) -- -- 50 50
50 50 50 50 weight *2 100 88 93 93 93 93 93 93 Weighting component
-- none none none none none none *3 Directionality 100 100 104 106
107 107 105 111 Carry distance 100 101 101 102 103 103 103 103
Scratch resistance 1 9 8 7 6 3 2 4 Durability Damaged? no yes no no
no no no no Number of hits 5000 1900 5000 5000 5000 5000 5000 5000
*1) (-)minus means that the extreme end of the heel-side sole plate
was positioned on the heel side the point SG. *2) weight of the
face component, hosel-and-heel component and rear component *3) A
weighting component having a length of 100 mm was disposed as shown
in FIGS. 4-6.
[0094] From the test results, it was confirmed that the weight
margins in Example heads Exs. 1 to 4 were remarkably increased when
compared with Ref. 1. Example heads Exs. 1 to 4 were improved in
the directionality when compared with Ref. 2. Example head Ex. 5
could be further improved in the directionality.
[0095] As described above, in the golf club head according to the
present invention, a major part of the club head is formed by a
magnesium alloy. Therefore, the weight margin is increased, without
deteriorating the ball hitting sound. Further, at least the major
part of the face portion, the major part of the sole portion and
the hosel portion are made of the titanium alloy(s). Therefore, the
durability of the head and the scratch resistance of the sole
portion can be improved. Furthermore, as the major part of the sole
portion is made of the titanium alloy as opposed to the magnesium
alloy, lowering of the center of gravity is facilitated.
[0096] The present invention is suitably applied to wood-type
hollow golf club heads. But, it is also possible to apply the
present invention to another type such as iron-type and
utility-type as far as the head has a hollow structure.
* * * * *